And when American scientists attempted to create sets that could emit shorter waves of thirty or forty centimeters, they discovered that their vacuum tubes lacked the power to send out a strong enough signal. “The big problem in radar is to generate enough power to get a detectable echo from a distant point,” Time magazine explained. “Of the total energy sent out in a radar beam scanning the skies, only a tiny fraction hits the target (e.g., a plane), and a much tinier echo gets back to the receiver.
